Ductile materials are manufactured as a semi-finished product in large quantities and large sizes, namely metallic materials. During the course of manufacture the need arises to achieve the required geometries by separating the preforms manufactured in multiple width or multiple length. Thus, for example, band-like semi-finished products are fabricated to the width and/or length required for the respective use through lengthwise and crosswise separation. In large scale production, cutting methods designed according to the roll-cutting principle are mostly used for this.
Sheet-metal band wound to a coil is thereby mostly separated into several narrow bands or strips of bands by longitudinal separating systems. The separation is done by a waste-free cutting with circular, rotating knives. Circular-knife scissors with a continuous operating shaft are equipped with circular knives, ring-like rollers and spacer sleeves. The method according to the state of the art is illustrated in FIG. 1.    [Source: Handbuch der Umformtechnik/Schuler GmbH Springer-Verlag Berlin Heidelberg New York, 1996, Page 286, Illustration 4.6.2]
A circular-knife scissors typical for the non-cutting longitudinal separation according to the roll-cutting principle thus consists essentially of symmetrical rotating knives which are fastened on an upper and on a lower cutter bar at a distance adapted to the thickness of the material to be separated, or, however, are clamped axially on knife driving shafts above and below the band. The knives are axially adjusted to one another to a specific cutting space and vertically to a tool immersion depth. These values are determined by the nature of the material itself, its thickness and by the desired shaping of the cutting edge.
The arched cutting edge of an upper knife rolls on and then off the edge during cutting against the cutting edge of a lower knife. A portion of the material is sheared by the cooperating knives, the remaining material thickness breaks to complete separation.
This breaking portion is for many materials, depending on thickness, hardness and nature, approximately 20%-40% of the band thickness. The breaking zone naturally develops a heavily roughened forced breaking surface. Its design is determined by the essentially freely occurring process of breaking. Shape and dimension of the breaking zone therefore differ clearly from the shearing zone formed by the direct action of the tools, and the breaking zone ends automatically at the original surface in a cutting burr (FIG. 2).
The cutting burr is a highly hardened, sharp-edged material which extends beyond the contours of the ideally separated material. Shape and size of the burr are again strongly influenced by method parameters.
Burrs are undesired in every respect. They pose risks for injury in case of manual handling. During further processing burrs can increasingly create undesired wear and flitter or can cause damage to surrounding material through the cutting action of the burr. The burr, which always lies on an outer edge of the material is, during use, fundamentally a weak point. The tear formation often begins here in cases of dynamic and static loads. In the case of high demands on the alternating bending strength of especially narrow material strips there exist particularly high demands on the cutting quality. An unfavorable shape of the band edges in the shearing zone area, the rough breaking zone and the cutting burr particularly significantly influence the alternating bending strength. Therefore great efforts are directed to minimizing the burr formation and the low-cost finishing of separate, burr-containing bands is of great interest.
The undefined shape of the broken portion of the separating surface is a further deficiency of the otherwise so economical rolling knife technique. Therefore for various uses instead of the low-cost separated band-shaped semi-finished products there exists the demand for bands expensively finished by finish rolling of the edges. As an alternative press/pull products in wire form are also utilized, which right from the start have defined geometries in the entire cross section.